1. Field of the Invention
The present invention, in various embodiments, relates to drill bits for subterranean drilling and, more particularly, to a nozzle and sleeve assembly therefor, including an insert assembly including the nozzle and sleeve assembly and a method of manufacturing or retrofitting drill bits with the insert assembly.
2. State of the Art
Drill bits for subterranean drilling, such as drilling for hydrocarbon deposits in the form of oil and gas, conventionally include internal passages for delivering a solids-laden drilling fluid, or “mud,” to locations proximate a cutting structure carried by the bit. In fixed cutter, or so-called “drag” bits, the internal passages terminate proximate the bit face at locations of nozzles received in the bit body for controlling the flow of drilling mud used to cool the cutting structures (conventionally polycrystalline diamond compact (PDC) or other superabrasive cutting elements). Some drag bits, termed “matrix” bits, are fabricated using particulate tungsten carbide infiltrated with a molten metal alloy, commonly copper-based. Other drag bits comprise steel bodies machined from castings. Steel body drag bits are susceptible to erosion from high pressure, high flow rate drilling fluids, on both the face of the bit and the junk slots as well as internally. As a consequence, on the bit face and in other high-erosion areas, hardfacing is conventionally applied. Within the bit, erosion-resistant components such as nozzles and sleeves fabricated from tungsten carbide or other erosion-resistant materials are employed to protect the steel of the bit body.
As shown in FIG. 8 of the drawings, a conventional steel body bit 500 for use in subterranean drilling includes a plurality of nozzle assemblies, exemplified by illustrated nozzle assembly 501. The nozzle assembly 501 is a two-piece replaceable nozzle assembly, the first piece being a tubular tungsten carbide nozzle sleeve 502 that fits into a port 504 machined in the steel body bit 500, and is seated upon an annular shoulder 505 of port 504. The second piece is a tungsten carbide nozzle 503 having a restricted bore 513 that secures and retains the nozzle sleeve 502 within port 504 of the steel body bit 500 by threads 506, which engage mating threads on the wall of port 504. The sleeve 502 and the nozzle 503 are used to provide protection to the steel of steel body bit 500 through which port 504 extends against erosive drilling fluid effects by providing a hard, abrasion and erosion-resistant pathway from an inlet fluid chamber or center plenum 507 within the bit body to a nozzle exit 508. The nozzle sleeve 502 and nozzle 503 are replaceable should the drilling fluid erode or wear the parts within internal passage 509 extending through these components, or when a nozzle 503 having a different orifice size is desired; however, it is intended that the nozzle sleeve 502 and nozzle 503 will protect the surrounding steel of the bit body from all erosion.
When drilling fluid is present in the fluid chamber 507 when drilling is being conducted, it is under a pressure P1 that is greater than the pressure P2 in the passage 509 or at the nozzle exit 508. In order to prevent fluid flow under pressure P1 from bypassing passage 509, the nozzle 503 is formed as a replaceable piece that has threads 506, wherein the bottom of nozzle 503 is designed to seat on the top of sleeve 502 as threads 506 are made up with those on the wall of port 504. Annular flange of sleeve 502 is designed to seat upon annular shoulder 505 of the body of bit 500, so that the components arranged as shown in FIG. 8 prevent fluid flow and associated erosion from occurring through the junctions 510, 511, 512 between components. Further, the outer surface or wall of the nozzle 503 is in sealing contact with a compressed O-ring 514 disposed in an annular groove formed in the wall of port 504 to provide a fluid seal between the body bit 500 and the nozzle 503. The junctions 510, 511, 512 are filled with a joint compound (not shown), such as BAKER-LOK® compound, in order to fill and seal any gaps. However, while it is undesirable that fluid flow in gaps provided by imperfect junctions 510, 511, 512, erosion from such flow around the exterior of sleeve 502 due to the pressure differential between P1 and P2 has been observed therein due to variations in component dimensional tolerances, the failure of the joint compound to fill any gaps attributable to such variations, and the failure of O-ring 514 to provide any sealing effect for the sleeve 502 and its junction 511 with the nozzle 503 and at annular shoulder 505.
Accordingly, it would be desirable to design and provide a nozzle assembly that is more robust in the drilling fluid flow, pressure and composition conditions that are encountered in subterranean drilling operations. It would also be advantageous to provide a nozzle assembly of a design that is suitable for both replacement and retrofit applications for existing steel body bits as well as in the manufacture of new steel body bits without requiring complicated and costly manufacturing or remanufacturing techniques. It would also be advantageous to provide a nozzle assembly that reduces or eliminates the need for joint compound.